Scandium chloride, alkyl and phenyl complexes of diamido-donor ligands

Article abstract of DOI:10.1039/b209382k

Reactions of the lithiated diamido-pyridine and -amine ligands Li₂N₂^TMSN_py or Li₂N₂N^C2,TMS with ScCl₃ in tetrahydrofuran (THF) afforded the five-coordinate scandium ch

Full text of DOI:10.1039/b209382k

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Scandium chloride, alkyl and phenyl complexes of diamido-donor
ligands
Benjamin D. Ward,a Stuart R. Dubberley,a Aline Maisse-François,b Lutz H. Gade*b and
Philip Mountford*a
a Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford,
UK OX1 3QR. E-mail: Philip.Mountford@chem.ox.ac.uk
b Laboratoire de Chimie Organométallique et de Catalyse, UMR 7513, Institut Le Bel,
Université Louis Pasteur, 4, rue Blaise Pascal, 67000 Strasbourg, France.
E-mail: gade@chimie.u-strasbg.fr
Received 25th September 2002, Accepted 22nd October 2002
First published as an Advance Article on the web 14th November 2002
TMS
Reactions of the lithiated diamido-pyridine and -amine ligands Li2N2
N
py
or Li2N2NC2,TMS with ScCl3 in
TMS
tetrahydrofuran (THF) afforded the five-coordinate scandium chloride derivatives [Sc(N2 Npy)Cl(THF)] 1
TMS
and [Sc(N2NC2,TMS)Cl(THF)] 2 where N2
N
= MeC(2-C5H4N)(CH2NSiMe3)2 and N2NC2,TMS = Me3SiN-
py
(CH2CH2NSiMe3)2. The corresponding reactions of ScCl3 with the dilithium salts of the amino N-methylated
two-carbon analogue N2NC2,Me (N2NC2,Me = MeN(CH2CH2NSiMe3)2) or of the amino N-silylated three-carbon
chain analogue N2NC3,TMS (N2NC3,TMS = Me3SiN(CH2CH2CH2NSiMe3)2) afforded no tractable products. In
contrast, reaction of ScCl3with the homologous N-methylated three-carbon chain species Li2N2NC3,Me (N2NC3,Me
MeN(CH2CH2CH2NSiMe3)2) cleanly gave the THF-free dinuclear, chloride-bridged compound [Sc2(N2NC3,Me)2-
=
(µ-Cl)2] 3. The compounds 1–3 have been crystallographically characterised. Organometallic analogues of 1 and 2
RЈ
RЈ
have been prepared by protonolysis reactions of H2N2
N (N2 N = MeC(2-C5H4N)(CH2NRЈ)2 where RЈ = SiMe3,
py py
Tol (4-C6H4Me) or Mes (2,4,6-C6H2Me3)) and H2N2NC2,RЈ (RЈ = Me or SiMe3) with [ScR3(THF)2] (R = CH2SiMe3
RЈ
or Ph) in benzene which gave the five-coordinate alkyl or phenyl compounds [Sc(N2 Npy)R(THF)] (R = CH2SiMe3,
RЈ = SiMe3 4, Tol 5 or Mes 6; R = Ph, RЈ = SiMe3 7) and [Sc(N2NC2,RЈ)(CH2SiMe3)(THF)] (RЈ = Me 8 or SiMe3 9).
The compound 4 can also be prepared by the reaction of 1 with LiCH2SiMe3. Reaction of [Sc(CH2SiMe3)3(THF)2]
with H2N2NC3,Me afforded no tractable product, and with H2N2NC3,TMS in deuterobenzene the labile compound
[Sc(N2NC3,TMS)(CH2SiMe3)(THF)] 10 was observed by 1H NMR spectroscopy but could not be isolated. On one
Tol
occasion the THF-free dimeric alkyl species [Sc2(N2 Npy)2(CH2SiMe3)2] 11 was obtained. This compound possesses
Tol
one bridging and one terminal amido nitrogen per N2
N ligand. The X-ray crystal structures of 6 and 11 have been
py
determined. The monomeric compounds 1, 2 and 6 all have trigonal bipyramidal Sc centres in the solid state; the
neutral donors take up the axial sites, and the amido nitrogens and either Cl or CH2SiMe3 occupy the equatorial
ones.
most successful in supporting a range of different ancilliary
Introduction
ligands ‘X’. However, this tetradentate ligand is rather rigid and
in none of its chemistry to date10d,11 have we found evidence for
lability of the pyridyl donor to generate a potentially vacant
ligand site that might, in turn, allow for enhanced reactivity. We
were therefore interested to develop scandium systems sup-
ported by tridentate diamido-donor ligands. A number of
potential ligands of this type are available12 and the ones
chosen for this study are listed in Chart 2 along with the
abbreviations used herein.
The organometallic and related coordination chemistry of
scandium was for a number of years generally dominated by
mono- and bis-cyclopentadienyl complexes.1 Over the past dec-
ade, however, a number of new, ‘alternative’, supporting ligand
systems have started to emerge, including: the tetratolylporphy-
rin systems developed by Arnold et al.;2 the bis(benzamidinato)
compounds of Edelmann and Arnold;3 the recent NP2-donor
ligand-supported systems of Fryzuk et al.;4 the low-valent
sandwich and related complexes of Cloke and coworkers;1e,5 the
tris(pyrazolyl)hydroborate, ‘nacnac’ and other systems studied
by Piers et al.;6 Scott’s tris(amido)amine complexes,7 Bazan’s
boratobenzene complexes8 and Bercaw’s triazacyclononane
systems.9
We ourselves have recently been interested to develop the
organometallic and related chemistry of scandium in previously
unexplored or underdeveloped (so far as this element is con-
cerned) ligand environments. Chart 1 shows some of the systems
which are currenly being studied in one of our groups.10 Apart
from the neutral tris(3,5-dimethylpyrazolyl)methane-supported
complexes I, all of the systems shown have mono- or di-anionic,
tetradentate ligand sets (II–IV). So far, the diamido-diamine
ligand (2-C5H4N)CH2N(CH2CH2NSiMe3)2 in IV has been the
The diamido-pyridine systems MeC(2-C5H4N)(CH2NR)2
R
(abbreviated as N2 Npy) were first developed by us13 for R =
t
SiMe3 and SiMe2 Bu and have recently been adopted by
Schrock and coworkers for R = Mes and 3,5-dichlorophenyl.14
The diamido-amine systems RN(CH2CH2NSiMe3)2 (abbrevi-
ated as N2NC2,R) where R = Me or SiMe3 have been developed
by Bertrand and coworkers,15 Cloke et al.16 and Horton et al.17
We have recently been using some of these ligands in developing
early transition metal imido chemistry.18 Whereas the N2NC2,R
ligands possess two-carbon CH2CH2 linkers between the ter-
minal amido and central amino nitrogen donors, the bottom
ligands in Chart 2, namely RN(CH2CH2CH2NSiMe3)2 (abbre-
viated as N2NC3,R) where R = Me or SiMe3, feature three-
carbon linkers and provide overall a more flexible environment
DOI: 10.1039/b209382k
J. Chem. Soc., Dalton Trans., 2002, 4649–4657
This journal is © The Royal Society of Chemistry 2002
4649

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Scheme 1 Reactions of ScCl3 with lithiated diamido-pyridine or
-amine ligands. Additions were carried out in THF at Ϫ78 ЊC. See the
text and the Experimental section for further details.
Chart 1
only scandium chloride derivative of this ligand system
prepared to date is [Sc(N2 Npy)Cl(THF)] 1 obtained in 59%
TMS
isolated yield as a pale yellow air- and moisture-sensitive
solid. The NMR data for 1 show resonances attributable to a
TMS
κ3-coordinated N2
N
ligand and a coordinated THF
py
ligand. The geometry shown in Scheme 1 has been confirmed
by X-ray diffraction as discussed below.
Reaction of ScCl3 with Li2N2NC2,Me in THF under identical
conditions to those used for the synthesis of 1 afforded only
complex mixtures. However, reaction with the amino N-SiMe3
functionalised lithiated ligand Li2N2NC2,TMS did give modest
isolated yields of the highly soluble, five-coordinate THF
adduct [Sc(N2NC2,TMS)Cl(THF)] 2 which again has been struc-
turally characterised as discussed below. The 1H NMR
spectrum of 2 in C6D6 features, in addition to resonances for
THF, intense resonances for two types of SiMe3 group (ratio
18H:9H) at 0.28 and 0.14 ppm, and the CH2CH2 backbone
methylene hydrogens give rise to four sets of mutually coupled,
sharp multiplets.
Reaction of ScCl3 with the three-carbon chain, amino
N-SiMe3 functionalised Li2N2NC3,TMS gave only complex
mixtures, but with the less sterically demanding amino
N-methylated ligand homologue the dinuclear compound
[Sc2(N2NC3,Me)2(µ-Cl)2] 3 was obtained as a white solid in 80%
yield after work-up. The NMR data for 3 feature no resonances
for THF and suggest that the molecules possess C2v symmetry
in solution on the NMR timescale at room temperature. Thus
1
the SiMe3 groups appear as single resonances in the H and
Chart 2
13C{1H} NMR spectra, and the chemically inequivalent pro-
tons of each CH2CH2CH2 linkage give rise to six individual,
broad multiplets in the 1H spectrum in toluene-d8 at room tem-
perature. On cooling the NMR sample to 213 K the SiMe3
resonances decoalesced to form two singlets, and the 13C NMR
spectrum showed six independent methylene carbons for the
two, now inequivalent, CH2CH2CH2 linkages. The central
amino N-methyl group appears as only a unique singlet in both
than their two-carbon chain homologues.19 In this contribution
we describe the potential usefulness of the seven ligands in
Chart 2 in the organometallic and coordination chemistry of
scandium.
Results and discussion
1
the H and 13C{1H} NMR spectra. Overall therefore the low
The successful reactions between ScCl3 and certain of the lithi-
ated diamido-donor ligands are summarised in Scheme 1. The
additions were carried out in THF at Ϫ78 ЊC, and during the
reaction ScCl3 dissolved after addition of the lithiated amide: it
was not necessary to prepare and isolate the THF complex
[ScCl3(THF)3] beforehand. We have not yet been able to obtain
temperature data suggest a Ci or Cs symmetric structure for 3
(with two equivalent N2NC3,Me ligands) rather than the C2v
structure implied by the room temperature data. These results
are consistent with the solid state structure as discussed below.
TMS
The X-ray crystal structures of [Sc(N2 Npy)Cl(THF)] 1,
[Sc(N2NC2,TMS)Cl(THF)] 2 and [Sc2(N2NC3,Me)2(µ-Cl)2] 3 have
been determined and are shown in Figs. 1–3. Selected bond
lengths and angles are listed in Tables 1–3. The ranges for the
well-defined lithiated derivatives of the N-aryl-substituted
Ar
diamido-pyridine ligands N2
N (Ar = Tol or Mes) and so the
py
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TMS
Table 1 Selected bond distances (Å) and angles (Њ) for [Sc(N2 Npy)-
Cl(THF)] 1
Sc(1)–Cl(1)
Sc(1)–N(1)
Sc(1)–N(2)
2.4426(7)
2.025(2)
2.024(2)
Sc(1)–N(3)
Sc(1)–O(1)
2.288(2)
2.205(2)
Cl(1)–Sc(1)–N(1)
Cl(1)–Sc(1)–N(2)
N(1)–Sc(1)–N(2)
Cl(1)–Sc(1)–N(3)
N(1)–Sc(1)–N(3)
Sc(1)–N(1)–Si(1)
Sc(1)–N(1)–C(1)
Si(1)–N(1)–C(1)
135.79(6)
122.35(6)
100.57(7)
89.45(5)
82.53(7)
126.8(1)
N(2)–Sc(1)–N(3)
Cl(1)–Sc(1)–O(1)
N(1)–Sc(1)–O(1)
N(2)–Sc(1)–O(1)
N(3)–Sc(1)–O(1)
Sc(1)–N(2)–Si(2)
Sc(1)–N(2)–C(3)
Si(2)–N(2)–C(3)
86.54(7)
86.09(4)
96.25(7)
101.22(7)
172.22(6)
129.6(1)
114.62(13)
115.30(13)
114.67(13)
116.43(14)
Table 2 Selected bond distances (Å) and angles (Њ) for [Sc(N2NC2,TMS)-
Cl(THF)] 2
Sc(1)–Cl(1)
Sc(1)–O(1)
Sc(1)–N(1)
2.3982(6)
2.192(2)
2.044(2)
Sc(1)–N(2)
Sc(1)–N(3)
2.044(2)
2.456(2)
Cl(1)–Sc(1)–O(1)
Cl(1)–Sc(1)–N(1)
O(1)–Sc(1)–N(1)
Cl(1)–Sc(1)–N(2)
O(1)–Sc(1)–N(2)
Sc(1)–N(1)–Si(1)
Sc(1)–N(1)–C(1)
Si(1)–N(1)–C(1)
90.07(4)
122.74(5)
94.00(6)
118.24(5)
97.52(7)
134.0(1)
109.40(13)
116.07(14)
N(1)–Sc(1)–N(2)
Cl(1)–Sc(1)–N(3)
O(1)–Sc(1)–N(3)
N(1)–Sc(1)–N(3)
N(2)–Sc(1)–N(3)
Sc(1)–N(2)–Si(2)
Sc(1)–N(2)–C(4)
Si(2)–N(2)–C(4)
117.71(7)
102.45(4)
167.35(6)
77.85(6)
78.20(6)
130.4(1)
TMS
Fig. 1 Molecular structure of [Sc(N2 Npy)Cl(THF)] 1. Displace-
113.98(13)
114.02(14)
ment ellipsoids are drawn at the 20% probability level. H atoms omitted
for clarity.
Fig. 3 Molecular structure of one of the two crystallographically
independent molecules of [Sc2(N2NC3,Me)2(µ-Cl)2] 3 in the asymmetric
unit. Displacement ellipsoids are drawn at the 25% probability level.
H atoms omitted for clarity. Atoms carrying the suffix ‘A’ are related to
their counterparts by the symmetry operator [1 Ϫ x, 1 Ϫ y, Ϫz].
Fig. 2 Molecular structure of [Sc(N2NC2,TMS)Cl(THF)] 2. Displace-
ment ellipsoids are drawn at the 30% probability level. H atoms omitted
for clarity.
trigonal planar. There are some small but significant differences
between the two structures. As a consequence of the more con-
straining CH2CH2 linkages in 2 the amino nitrogen N(3) is not
quite able to occupy properly the axial position so that the
N(3)–Sc(1)–O(1) angle of 167.35(6)Њ is somewhat less than the
ideal value of 180Њ, and the N(3)–Sc(1)–Cl(1) angle of
102.45(4)Њ is somewhat larger than the ideal 90Њ required for a
trigonal bipyramidal geometry. In 1 the corresponding angles
are 172.22(6) and 89.45(5)Њ which are somewhat closer to the
ideal values. The very different Sc(1)–N(3) distances of 2.288(2)
and 2.456(2) Å in 1 and 2 underscore the differences deduced by
examination of the angles, and also reflect the better donor
ability of pyridyl nitrogen atoms compared with that of SiMe3-
substituted amines. Interestingly, although the Sc–Cl distance
of 2.4426(7) Å in 1 is considerably longer than that of 2.3982(6)
Å in 2 the Sc–O distances of 2.205(2) and 2.192(2) are only
Sc–O, Sc–Namide, Sc–Namine, Sc–Npyridyl and Sc–Cl distances, as
well as those within the ligands themselves, are unremarkable
and within ranges previously reported.20
TMS
The structures of [Sc(N2 Npy)Cl(THF)] 1 (Fig. 1) and
[Sc(N2NC2,TMS)Cl(THF)] 2 (Fig. 2) confirm the five-coordinate
monomeric motifs suggested in Scheme 1 on the basis of the
NMR data. In each compound the diamido-donor ligand
adopts a fac, κ3 coordination mode. The THF ligands lie trans
to the neutral N-donor atoms. The Sc atoms possess approxi-
mately trigonal bipyramidal coordination geometries with the
amido N and the Cl atoms lying in the equatorial plane. The
geometry at the amido nitrogens themselves is approximately
J. Chem. Soc., Dalton Trans., 2002, 4649–4657
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Table 3 Selected bond distances (Å) and angles (Њ) for [Sc2(N2NC3,Me)2-
(µ-Cl)2] 3. The values in brackets correspond to the other crystallo-
graphically independent molecule in the asymmetric unit
Sc(1)–Cl(1)
Sc(1)–Cl(1A)
Sc(1)–N(1)
Sc(1)–N(2)
Sc(1)–N(3)
2.5208(6)
2.6162(6)
2.020(2)
2.318(2)
2.029(2)
[2.5217(6)]
[2.6162(6)]
[2.026(2)]
[2.325(2)]
[2.021(2)]
Cl(1)–Sc(1)–Cl(1A)
Cl(1)–Sc(1)–N(1)
Cl(1A)–Sc(1)–N(1)
Cl(1)–Sc(1)–N(2)
Cl(1A)–Sc(1)–N(2)
N(1)–Sc(1)–N(2)
Cl(1)–Sc(1)–N(3)
Cl(1A)–Sc(1)–N(3)
N(1)–Sc(1)–N(3)
N(2)–Sc(1)–N(3)
Sc(1)–N(1)–Si(1)
Sc(1)–N(1)–C(1)
Si(1)–N(1)–C(1)
Sc(1)–N(3)–Si(2)
Sc(1)–N(3)–C(6)
Si(2)–N(3)–C(6)
80.66(2)
112.36(5)
100.73(5)
88.52(4)
168.61(4)
86.62(6)
127.74(5)
96.73(5)
119.29(7)
87.06(6)
127.96(9)
114.23(13)
117.80(13)
127.64(9)
113.71(12)
118.56(13)
[80.78(2)]
[128.72(5)]
[95.83(5)]
[88.71(5)]
[168.59(5)]
[87.25(6)]
[111.09(5)]
[100.74(5)]
[119.71(7)]
[87.13(6)]
[127.70(9)]
[114.18(12)]
[117.71(13)]
[128.8(1)]
[115.06(13)]
[116.05(13)]
marginally different despite the quite different donor abilities of
the atoms trans to the THF ligands in each case. Possibly the
shorter Sc–Namide distances (avg. 2.024 Å) in 1 compared to
those in 2 (avg. 2.044 Å) are the origin of the longer Sc–Cl
distance in 1.
Scheme 2 Reactions of [Sc(CH2SiMe3)3(THF)2] or [ScPh3(THF)2]
with diamino-pyridine or -amine ligand precursors. Additions were
carried out in C6H6 at 7 ЊC (or in C6D6 at rt). See the text and the
Experimental section for further details.
Molecules of [Sc2(N2NC3,Me)2(µ-Cl)2] 3 (Fig. 3) possess
crystallographically-imposed Ci symmetry. There are two
crystallographically-independent half-molecules of 3 in the
asymmetric unit but there are no very significant differences
between them. The N2NC3,Me ligands adopt κ3 coordination
modes as found for the diamido-donor ligands in 1 and 2. The
geometry at the scandium centres is also approximately trigonal
bipyramidal with the two amido nitrogens and one of the Cl
ligands occupying the equatorial plane. The geometry at the
amido nitrogens is again approximately trigonal planar. The
Sc–Cl distances are somewhat longer than those in 1 or 2 as
expected for such bridging groups.
the corresponding alkyl derivatives [Sc(N2 Npy)(CH2SiMe3)-
R
(THF)] (4–6) in 57–82% yields. For comparison, the reaction of
TMS
LiCH2SiMe3 with [Sc(N2 Npy)Cl(THF)] 1 was carried out on
the NMR tube scale in C6D6 at room temperature. After
30 min, 4 was formed in quantitative yield as the only organo-
metallic product. The formation of other diamido-donor-
supported scandium alkyl complexes by chloride ligand
metathesis was not attempted, although this might well provide
a useful alternative route to the organoscandium complexes.
TMS
The reaction of H2N2
N with the triphenyl complex [ScPh3-
py
TMS
(THF)2] afforded the expected product, namely [Sc(N2 Npy)-
Ph(THF)] (7), in the slightly lower yield of 49%. But this com-
pound, like the starting material [ScPh3(THF)2], is thermally
unstable at room temperature, quite rapidly decomposing to
unknown products and benzene. For this reason it was decided
not to prepare other phenyl scandium derivatives in this study.
Scheme 2 also summarises the reactions of the protonated
forms of the other diamido-amine donor ligands with [Sc(CH2-
SiMe3)3(THF)2]. The reactions with the protonated two-carbon
linker ligands H2N2NC2,R yielded [Sc(N2NC2,R)(CH2SiMe3)-
(THF)] (R = Me 8 or SiMe39) in ca. 50% yields as very soluble
pale yellow or white solids. Reaction of [Sc(CH2SiMe3)3(THF)2]
with the three-carbon protonated ligands H2N2NC3,R (Scheme
2) gave no tractable product for R = Me. With the N-SiMe3-
At first sight the scandium centres in 3 appear to be a good
deal more crowded than those in the other two compounds, but
closer inspection shows that the conformations of the two
CH2CH2CH2NSiMe3 ‘arms’ in each ligand is different. Thus
the SiMe3 group bonded to N(3) [or N(3A) at Sc(1A)] is
oriented towards the other scandium, whereas that attached
to N(1) [or N(1A)] bends away into available space. This
greater flexibility appears to allow the two monomeric
Sc(N2NC3,Me)Cl fragments to approach each other more
comfortably than they would in the cases of the hypothetical
TMS
THF-free moieties Sc(N2 Npy)Cl and Sc(N2NC2,TMS)Cl,
since in 1 and 2 the two SiMe3 groups are oriented ‘forwards’
[i.e. towards Cl(1)] in each case. The ‘twisted’ conformation of
the N2NC3,Me ligands found in the solid state for 3 explains
fully the low temperature solution NMR data described above.
In related crystallographic studies19 we have found that in both
[Zr(N2NC3,Me)Cl2] and [Zr(N2NC3,Me)(CH2Ph)2] the CH2CH2-
CH2NSiMe3 ‘arms’ of N2NC3,Me also adopt similar conform-
ations to those in 3 and so this feature is not therefore just
attributable to the comparatively small covalent radius of
scandium.
functionalised H2N2NC3,TMS
a
product [Sc(N2NC3,TMS)-
(CH2SiMe3)(THF)] 10 could be observed (with concomitant
evolution of SiMe4) on the NMR tube scale in C6D6 but could
not be made on a preparative scale.
The NMR spectra of 4–9 are fully consistent with the struc-
tures proposed in Scheme 2. Resonances attributed to diamido-
donor ligands, coordinated THF, and either CH2SiMe3 or
1
Ph (for 7) groups are readily visible in the H and 13C NMR
spectra. The THF ligand OCH2 protons (i.e. adjacent to oxy-
Scheme 2 summarises the syntheses of organo-scandium
compounds supported by the various diamido-donor ligands.
Protonolysis routes from [Sc(CH2SiMe3)3(THF)2]21 and, in one
gen) in the alkyl complexes of the amide N-arylated ligands
Ar
N2
N
(i.e. 5 and 6) appear somewhat more upfield of those
py
of the amide N-SiMe3-functionalised ligands (i.e. 4, 8 and 9).
This is attributed to anisotropic shielding effects from the tolyl
or mesityl aromatic rings for these ligands. This feature is
instance, [ScPh3(THF)2]22 were chosen so as to avoid needing to
Ar
access the lithiated N2
N
(Ar = Tol or Mes) ligands for the
py
Mes
reasons mentioned above.
Reactions of [Sc(CH2SiMe3)3(THF)2] with H2N2 Npy (R =
supported by the X-ray structure of [Sc(N2 Npy)(CH2SiMe3)-
R
(THF)] 6 (Fig. 4; selected bond lengths and angles are listed in
SiMe3, Tol or Mes) in benzene at 7 ЊC proceed smoothly to form
Table 4).
4652
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Mes
Table 4 Selected bond distances (Å) and angles (Њ) for [Sc(N2 Npy)-
(CH2SiMe3)(THF)] 6
Sc(1)–N(1)
Sc(1)–N(2)
Sc(1)–N(3)
2.090(3)
2.281(3)
2.018(3)
Sc(1)–C(28)
Sc(1)–O(1)
2.295(3)
2.222(2)
N(1)–Sc(1)–N(2)
N(1)–Sc(1)–N(3)
N(1)–Sc(1)–C(28)
N(1)–Sc(1)–O(1)
N(2)–Sc(1)–N(3)
82.5(1)
98.1(1)
148.9(1)
92.2(1)
85.4(1)
N(2)–Sc(1)–C(28)
N(2)–Sc(1)–O(1)
N(3)–Sc(1)–C(28)
N(3)–Sc(1)–O(1)
C(28)–Sc(1)–O(1)
93.8(1)
171.29(9)
112.4(1)
102.2(1)
87.2(1)
Tol
Table 5 Selected bond distances (Å) and angles (Њ) for [Sc2(N2 Npy)2-
(CH2SiMe3)2] 11
Sc(1)–N(1)
Sc(1)–N(1A)
Sc(1)–N(2)
2.201(2)
2.285(2)
2.064(2)
Sc(1)–N(3)
Sc(1)–C(24)
2.280(2)
2.248(2)
N(1)–Sc(1)–N(1A)
N(1)–Sc(1)–N(2)
N(1A)–Sc(1)–N(2)
N(1)–Sc(1)–N(3)
N(3)–Sc(1)–C(24)
Sc(1)–N(1)–Sc(1A)
Sc(1)–N(1)–C(1)
Sc(1A)–N(1)–C(1)
Sc(1)–N(1)–C(10)
81.74(8)
99.66(8)
103.45(7)
78.75(7)
94.48(9)
98.26(8)
108.34(14)
110.99(14)
107.45(14)
N(1A)–Sc(1)–N(3)
N(2)–Sc(1)–N(3)
N(1)–Sc(1)–C(24)
N(1A)–Sc(1)–C(24)
N(2)–Sc(1)–C(24)
C(1)–N(1)–C(10)
Sc(1)–N(2)–C(3)
Sc(1)–N(2)–C(17)
C(3)–N(2)–C(17)
160.41(7)
81.76(7)
141.23(8)
99.60(8)
117.27(9)
116.0(2)
118.5(2)
126.6(2)
114.7(2)
Tol
Fig. 5 Molecular structure of [Sc2(N2 Npy)2(CH2SiMe3)2] 11. Dis-
placement ellipsoids are drawn at the 20% probability level. H atoms
and residual toluene molecules of crystallisation omitted for clarity.
Atoms carrying the suffix ‘A’ are related to their counterparts by the
symmetry operator [2 Ϫ x, Ϫy, 1 Ϫ z].
Sc(1A)–N(1)–C(10) 114.06(14)
be monomeric. Unlike THF-free, dimeric [Sc2(N2NC3,Me)2-
(µ-Cl)2] 3 in which the otherwise four-coordinate scandium
atoms are bridged by Cl ligands, in 11 they are bridged by one
Tol
of the amido nitrogen atoms of each N2
N ligand. The scan-
py
dium centres again possess trigonal bipyramidal geometries
with [at Sc(1)] the axial sites being occupied by N(1A) and N(3),
the Npyridyl donor. The equatorial sites are taken up by one ter-
minal and one bridging amido nitrogen [namely N(2) and N(1),
respectively] and the CH2SiMe3 ligand itself. The Sc(1)–N(1A)
(axial) bond length of 2.285(2) is nearly 0.1 Å longer than
Sc(1)–N(1) (equatorial) implying that the former is more dative
in nature. A similar trend in the Sc–Cl distances was seen in
dinuclear 3 above and is consistent with the general observation
that anionic donors in these d0 MX3L2-type systems prefer
equatorial coordination sites.23
Conclusions
Mes
We have employed a range of diamido-donor ligands in the
context of developing new organometallic and coordination
chemistry of scandium. Such compounds are fairly straight-
forward to prepare, but there are clear dependencies on the
backbone chain length and amino N-substituent of the
diamido-amine ligands N2NCn,R (n = 2 or 3, R = Me or SiMe3).
We are continuing to explore the reactivity of the new com-
pounds and ligands reported herein and also those in Charts 1
and 2, and will report on these studies, along with related work
for the heavier Group 3 and lanthanide elements, in due course.
Fig.
4
Molecular structure of [Sc(N2 Npy)(CH2SiMe3)(THF)] 6.
Displacement ellipsoids are drawn at the 20% probability level. H atoms
and residual Et2O molecule of crystallisation omitted for clarity.
The scandium centre in 6 again adopts a trigonal bipyram-
idal geometry with the pyridyl and THF donors occupying
axial coordination sites. The distances and angles in 6 are fairly
comparable to those in the related compound [Sc(N2
Npy)Cl(THF)] 1 discussed above. The Sc–C distance of 2.295(3)
is well within the expected ranges.20 The Sc–Namide distances of
2.018(3) and 2.09(3) Å are significantly different from each
other (in 1 they are ca. 2.024 Å and equivalent within error).
This is possibly associated with the orientation of the alkyl
SiMe3 substituent which orients itself more towards the mesityl
group bonded to N(1) [which in turn has the longer bond length
to Sc(1)].
On one occasion a few diffraction-quality crystals of the
highly insoluble dimer [Sc2(N2 Npy)2(CH2SiMe3)2] 11 were
obtained. The molecular structure is shown in Fig. 5 and
selected bond lengths and angles are listed in Table 5. The
compound 11 is the THF-free version of [Sc(N2 Npy)-
TMS
-
Experimental
General methods and instrumentation
All manipulations were carried out using standard Schlenk
line or drybox techniques under an atmosphere of argon or of
dinitrogen. Solvents were predried over activated 4 Å molecular
sieves and were refluxed over appropriate drying agents under a
dinitrogen atmosphere and collected by distillation. Deuterated
solvents were dried over appropriate drying agents, distilled
under reduced pressure, and stored under dinitrogen in Teflon
Tol
Tol
(CH2SiMe3)(THF)] 5 which, by analogy with 6, is assumed to
J. Chem. Soc., Dalton Trans., 2002, 4649–4657
4653

View Article Online
valve ampoules. NMR samples were prepared under dinitrogen
pale yellow solid. Yield 358 mg (59%). Crystals suitable for
X-ray diffraction were grown from a saturated solution in hex-
anes at Ϫ30 ЊC over 18 h.
in 5 mm Wilmad 507-PP tubes fitted with J. Young Teflon
1
valves. H, 13C{1H}, and 13C NMR spectra were recorded on
Varian Unity Plus 500, Bruker AC 200 and Varian Mercury-VX
1H NMR data (C6D6, 500.0 MHz, 298 K): 9.60 [1 H, ddd, H6,
3J (H5H6) = 5.4 Hz, 4J (H4H6) = 1.9 Hz, 5J (H3H6) = 0.7 Hz], 7.03
[1 H, td, H4, 3J (H3H4H5) = 6.8 Hz, 4J (H4H6) = 1.7 Hz],
1
spectrometers. H and 13C assignments were confirmed when
necessary with the use of NOE, DEPT-135, DEPT-90, DEPT-
45, and two dimensional 1H–1H and 13C–1H NMR experiments.
All spectra were referenced internally to residual protio-solvent
(1H) or solvent (13C) resonances and are reported relative to
tetramethylsilane (δ = 0 ppm). Chemical shifts are quoted
in δ (ppm) and coupling constants in Hz. Infrared spectra
were prepared as Nujol mulls between NaCl or KBr plates
or as KBr pellets and were recorded on Perkin-Elmer 1600 and
1710 series spectrometers. Infrared data are quoted in wave-
numbers (cmϪ1). Mass spectra were recorded by the mass
spectrometry service of the University of Oxford’s Inorganic
Chemistry Laboratory. Combustion analyses were recorded by
the analytical services of the University of Oxford’s Inorganic
Chemistry Laboratory, the Service Commun de Microanalyse
at Strasbourg or Mikroanalytisches Labor Pascher, Germany.
Despite all of the compounds being spectroscopically pure,
several of them gave carbon elemental analyses that were con-
sistently and persistently low. We attribute this to incomplete
sample combustion and carbide formation.
3
6.95 [1 H, d, H3, J (H3H4) = 8.1 Hz], 6.49 [1 H, ddd, H5,
3J = 7.6 Hz, 3J = 5.5 Hz, 4J (H3H5) = 1.1 Hz], 4.14 (4 H, t, OCH2,
2
3J = 6.6 Hz), 3.76 (2 H, d, CHH, J = 12.2 Hz), 3.17 (2 H, d,
CHH, 2J = 12.2 Hz), 1.30 (4 H, m, OCH2CH2), 1.16 (3 H, s, Me
TMS
of N2 Npy), 0.04 (18 H, s, SiMe3). 13C{1H} NMR data (C6D6,
125.7 MHz, 298 K): 162.4 (C2), 147.8 (C6), 138.5 (C4), 121.1
(C5), 120.5 (C3), 72.3 (OCH2), 62.4 (CH2NSiMe3), 48.8
TMS
[C(CH2NSiMe3)2], 25.3 (OCH2CH2), 24.7 (Me of N2 Npy),
0.2 (SiMe3). IR data (KBr plates, Nujol, cmϪ1): 2672 (w), 1600
(m), 1568 (w), 1296 (w), 1258 (s), 1242 (s), 1134 (w), 1088 (m),
1066 (s), 1018 (m), 922 (s), 894 (s), 880 (m), 826 (s), 776 (m), 722
(w). Anal. Found (calc. for C19H37ClN3OScSi2): C 49.1 (49.6), H
8.3 (8.1), N 9.7 (9.1)%.
[Sc(N2NC2,TMS)Cl(THF)] (2)
ScCl3 (200 mg, 1.32 mmol) was slurried in THF (15 ml) and
cooled to Ϫ78 ЊC. To this vigorously stirred solution was added
a solution of Li2N2NC2,TMS (438 mg, 1.32 mmol) in THF (15 ml)
dropwise over 10 min. The reaction was allowed to warm to rt
and stirred for a further 2 h, after which time all of the ScCl3
had dissolved. The solvent was removed under reduced pressure
and the solid residue extracted with benzene (20 ml), filtered,
and the solvent removed under reduced pressure. Recrystallis-
ation from a saturated pentane solution afforded 2 as a white
solid. Yield 173 mg (28%). Crystals suitable for X-ray diffrac-
tion were grown from a saturated pentane solution at Ϫ30 ЊC
over 4 days.
Literature preparations
The compounds [Sc(CH2SiMe3)3(THF)2],21 [ScPh3(THF)2],22
TMS
TMS
Mes
H2N2 Npy,13 Li2N2 Npy,13 H2N2 Npy,14 H2N2NC2,TMS 16
,
Li2N2NC2,TMS 16
,
H2N2NC2,Me 15
,
Li2N2NC2,Me 19
,
H2N2NC3,TMS 19
were pre-
,
Li2N2NC3,TMS 19
,
H2N2NC3,Me 19
,
and Li2N2NC3,Me 19
,
pared as reported previously.
H2N2TolNpy
1H NMR data (C6D6, 500.0 MHz, 298 K): 3.93 (2 H, m,
NCH2), 3.69 (4 H, br. s, OCH2), 2.98 (2 × 2 H, overalapping
2 × m, NCH2), 2.35 (2 H, d, NCH2, 2J = 11.8 Hz), 1.22 (4 H, m,
OCH2CH2), 0.28 (9 H, s, amine-SiMe3), 0.14 (18 H, s, amide-
SiMe3). 13C{1H} NMR data (C6D6, 125.7 MHz, 298 K): 72.1
(OCH2), 61.5 (NCH2), 47.5 (NCH2), 25.3 (OCH2CH2), 1.4
(amide-SiMe3), Ϫ1.2 (amine-SiMe3). IR data (KBr pellet,
cmϪ1): 2952 (s), 2896 (m), 2838 (m), 1586 (w), 1448 (m), 1400
(m), 1342 (m), 1250 (s), 1072 (s), 1030 (m), 938 (s), 912 (s),
786 (m), 754 (m), 680 (m), 618 (w), 508 (w), 450 (w), 436 (w),
402 (w). Anal. Found (calc. for C17H43ClN3OScSi3): C 42.4
(43.4), H 9.2 (9.2), N 9.1 (8.9)%. Accurate mass FI-MS for
fragment [Sc(N2NC2,TMS)Cl]ϩ: Found (calc. for C13H35ClN3-
ScSi3): 397.1392 (397.1386).
A Schlenk flask was charged with MeC(2-C5H4N)(CH2NH2)2
(2.07 g, 12.5 mmol),13 4-bromotoluene (4.27 g, 25 mmol),
[Pd2(dba)3] (0.17 g, 0.19 mmol, dba = dibenzylideneacetone),
racemic BINAP (0.29g, 0.47 mmol) and NaOtBu (5.40 g, 56.2
mmol) which were suspended in toluene (150 ml). After stirring
the reaction mixture at 110 ЊC for 24 h, the volatiles were
removed in vacuo and the brown residue redissolved in Et2O (75
ml). The resulting solution was washed with H2O (3 × 30 ml)
and then with a saturated aqueous solution of NaCl (3 × 30
ml). After drying over MgSO4 and removal of the volatiles the
resulting pale brown material was extracted into pentane (3 × 5
Tol
ml). After storing at Ϫ30 ЊC for 24 h, H2N2
N crystallized as
py
a pale yellow solid. Yield 66%.
1H NMR data (CDCl3, 200.0 MHz, 298 K): 8.65 (1 H, ddd,
3
4
5
3
H6, J = 4.8, J = 1.9, J = 1.0 Hz), 7.68 (1 H, dt, H4, J = 7.4,
4J = 1.9 Hz), 7.41 (1 H, m, H3), 7.21 (1 H, m, H5), 6.99 (4 H, d,
o-C6H4Me, 3J = 8.1 Hz), 6.56 (4 H, d, m-C6H4Me, 3J = 8.1 Hz),
4.17 (2 H, s, NH), 3.59 (2 H, d, CHH, 2J = 12.2 Hz), 3.53 (2 H,
[Sc2(N2NC3,Me)2(ꢀ-Cl)2] (3)
ScCl3 (200 mg, 1.32 mmol) was slurried in THF (20 ml) and
cooled to Ϫ78 ЊC for the dropwise addition of Li2N2NC3,Me
(412 mg, 1.32 mmol) in THF (20 ml). The reaction was allowed
to warm to rt and stirred for a further 3 h. The solvent was
removed under reduced pressure, the residue extracted with
benzene (2 × 20 ml) and filtered to remove LiCl. The solvent
was removed under reduced pressure to afford 3 as a white
solid. Yield 389 mg (80%). Crystals suitable for X-ray diffrac-
tion were grown by the slow cooling of a saturated solution in
hot hexanes to Ϫ30 ЊC over 18 h.
2
d, CHH, J = 12.2 Hz), 2.25 (6 H, s, C6H4Me), 1.53 (3 H, s,
Me of N2 Npy). 13C{1H} NMR data (CDCl3, 52.3 MHz, 298
Tol
K): 164.4 (C2), 148.9 (C6), 146.7 (ipso-C6H4Me), 136.7 (C4),
129.7 (o-C6H4Me), 126.5 (p-C6H4Me), 121.3, 121.6 (C3,5), 113.3
(m-C6H4Me), 52.8 [(CH2NTol)], 45.6 [C(CH2NTol)2], 23.2 (Me
Tol
of N2 Npy), 23.2 (C6H4Me). Anal. Found (calc. for C23H27N3):
C 79.8 (80.0), H 8.0 (7.9), N 11.9 (12.2)%.
1H NMR data (toluene-d8, 500.0 MHz, 298 K): 3.53 (4 H, br.
s, CH2), 3.35 (4 H, br. s, CH2), 2.73 (2 × 4 H, 2 × overlapping br.
s, CH2), 2.14 (6 H, s, NMe), 1.52 (4 H, br. s, CH2), 1.42 (4 H, br.
s, CH2), 0.29 (36 H, s, SiMe3). 1H NMR data (toluene-d8, 500.0
MHz, 213 K): 3.89 (2 H, t, CH2, 2J = 13.2 Hz), 3.57 (2 H, t, CH2,
2J = 14.7 Hz), 3.41 (2 H, t, CH2, 2J = 12.4 Hz), 3.14–3.01 (6 H,
overlapping m, CH2), 2.01 (6 H, s, NMe), 1.70–1.65 (4 H, over-
lapping m, CH2), 1.39–1.21 (8 H, overlapping m, CH2), 0.41
(18 H, s, SiMe3), 0.39 (18 H, s, SiMe3). 13C{1H} NMR data
(toluene-d8, 125.7 MHz, 213 K): 62.2 (CH2), 58.9 (CH2), 47.1
[Sc(N2TMSNpy)Cl(THF)] (1)
ScCl3 (200 mg, 1.32 mmol) was slurried in THF (20 ml) and
cooled to Ϫ78 ЊC. To this vigorously stirred solution was added
TMS
a solution of Li2N2
N (425 mg, 1.32 mmol) in THF (20 ml)
py
dropwise over 10 min. The reaction was allowed to warm to rt
and stirred for a further 2 h, after which time all of the ScCl3
had dissolved. The solvent was removed under reduced pressure
and the solid residue extracted with benzene (20 ml), filtered,
and the solvent removed under reduced pressure to afford 1 as a
4654
J. Chem. Soc., Dalton Trans., 2002, 4649–4657

View Article Online
(CH2), 45.4 (CH2), 44.1 (NMe), 30.6 (CH2), 29.7 (CH2), 1.8
(SiMe3), 1.6 (SiMe3). IR data (KBr pellet, cmϪ1): 2854 (s), 2812
(s), 2740 (w), 2664 (w), 1922 (w), 1870 (w), 1592 (s), 1488 (s),
1438 (m), 1396 (w), 1242 (s), 1208 (s), 1174 (s), 1004 (s), 950 (s),
918 (m), 794 (m), 744 (m), 694 (m), 680 (m), 626 (w), 610 (w),
530 (m), 510 (w), 464 (w), 446 (w), 424 (w), 408 (m). Anal.
Found (calc. for C26H66Cl2N6Sc2Si4): C 42.4 (42.4), H 9.3 (9.1),
N 11.4 (11.4)%. EI-MS (m/z): 367 (30%) [½ M]ϩ, 352 (30%)
[½ M Ϫ Me]ϩ, 332 (20%) [½ M Ϫ Cl]ϩ, 221 (15%) [½ M Ϫ 2
SiMe3]ϩ.
112.5 (m-C6H5Me), 71.6 (OCH2), 62.3 (CH2NSiMe3), 44.1
Tol
[C(CH2NSiMe3)2], 26.1 (Me of N2 Npy), 25.0 (OCH2CH2),
20.7 (C6H4Me), 4.4 (SiMe3), Ϫ0.1 (CH2SiMe3). IR data
(KBr pellet, cmϪ1): 2944 (s), 2916 (s), 2858 (s), 2804 (s),
2734 (w), 2558 (w), 1854 (w), 1610 (s), 1570 (m), 1554 (m),
1504 (s), 1476 (m), 1388 (m), 1288 (s), 1262 (s), 1184 (m),
1146 (m), 1114 (m), 1060 (w), 972 (w), 864 (s), 806 (s), 770 (s),
752 (w), 678 (w), 648 (w), 606 (w), 588 (w), 514 (w), 472 (w).
Anal. Found (calc. for C31H44N3OScSi): C 67.6 (67.9), H 7.6
(8.1), N 7.7 (7.7)%.
Mes
[Sc(N2TMSNpy)(CH2SiMe3)(THF)] (4) from H2N2TMSNpy and
[Sc(CH2SiMe3)3(THF)2]
[Sc(N2 Npy)(CH2SiMe3)(THF)] (6)
[Sc(CH2SiMe3)3(THF)2] (200 mg, 0.444 mmol) was dissolved in
benzene (20 ml) and cooled to 7 ЊC for the dropwise addition of
[Sc(CH2SiMe3)3(THF)2] (200 mg, 0.473 mmol) was dissolved in
Mes
H2N2
N
(178 mg, 0.444 mmol) in benzene (20 ml). The
benzene (20 ml) and cooled to 7 ЊC for the dropwise addition of
py
TMS
resulting pale yellow solution was allowed to warm to rt and
stirred for 1 h. The volatiles were removed under reduced pres-
sure to afford 6 as a pale yellow solid. Yield 219 mg (82%).
Crystals suitable for X-ray diffraction study were grown from a
saturated solution of 6 in diethyl ether on cooling to Ϫ20 ЊC for
18 h.
H2N2
N
(147 mg, 0.473 mmol) in benzene (20 ml). The
py
resulting pale yellow solution was allowed to warm to rt and
stirred for 1 h. The volatiles were removed under reduced pres-
sure to afford 4 as a pale yellow solid. Yield 138 mg (57%).
1H NMR data (C6D6, 500.0 MHz, 298 K): 9.02 [1 H, d, H6,
3
3J (H5H6) = 4.6 Hz], 7.06 [1 H, td, H4, J (H3H4H5) = 7.5 Hz,
1H NMR data (C6D6, 500.0 MHz, 298 K): 9.24 [1 H, dd, H6,
3
4J (H4H6) = 1.2 Hz], 6.98 [1 H, dd, H3, J (H3H4) = 8.3 Hz,
4
3J (H5H6) = 5.4 Hz, J (H4H6) = 2.0 Hz], 7.11 [1 H, td, H4,
3
4J (H3H5) = 1.0 Hz], 6.60 [1 H, td, H5, J (H4H5H6) = 5.4 Hz,
4
3J (H3H4H5) = 7.8 Hz, J (H4H6) = 2.0 Hz], 6.97 [1 H, d, H3,
4J (H3H5) = 1.3 Hz], 4.00 (4 H, br. s, OCH2), 3.61 (2 H, d,
NCHH, 2J = 12.2 Hz), 3.17 (2 H, d, NCHH, 2J = 12.2 Hz), 1.34
3J (H3H4) = 8.3 Hz], 6.90 (4 H, s C6H2Me3), 6.75 [1 H, ddd, H5,
3J (H5H6) = 5.4 Hz, 3J (H4H5) = 7.3 Hz, 4J (H3H5) = 1.0 Hz], 4.01
(2 H, d, CHH, 2J = 11.7 Hz), 3.46 (4 H, t, OCH2, 3J = 6.3 Hz),
TMS
(4 H, br. s, OCH2CH2), 1.15 (3 H, s, Me of N2 Npy), 0.42
(9 H, s, CH2SiMe3), 0.04 (18 H, s, NSiMe3), Ϫ0.39 (2 H, s,
CH2SiMe3). 13C{1H} NMR data (C6D6, 125.7 MHz, 298 K):
163.3 (C2), 146.2 (C6), 138.8 (C4), 120.8 (C3), 120.6 (C5), 71.4
(OCH2), 62.5 (CH2NSiMe3), 48.5 [C(CH2NSiMe3)2], 25.3
2
2.88 (2 H, d, CHH, J = 11.7 Hz), 2.31 (12 H, s, o-C6H2Me3),
Mes
2.18 (6 H, s, p-C6H2Me3), 1.15 (3 H, s, Me of N2 Npy), 1.05
(4 H, m, OCH2CH2), 0.27 (9 H, s, SiMe3), Ϫ0.51 (2 H, s,
CH2SiMe3). 13C{1H} NMR data (C6D6, 125.7 MHz, 298 K):
163.8 (C2), 151.4 (ipso-C6H2Me3), 146.8 (C6), 138.7 (C4), 133.5
(o-C6H2Me3), 130.2 (p-C6H2Me3), 129.5 (m-C6H2Me3), 121.1
(C5), 121.0 (C3), 70.5 (OCH2), 66.8 (CH2NSiMe3), 46.7
TMS
(OCH2CH2), 25.0 (Me of N2 Npy), 5.0 (CH2SiMe3), 0.6
(NSiMe3), 0.2 (CH2SiMe2). IR data (KBr pellet, cmϪ1): 2946
(s), 2892 (m), 2794 (m), 2732 (w), 2674 (w), 1602 (m), 1570 (w),
1474 (m), 1386 (m), 1366 (w), 1366 (w), 1346 (w), 1240 (s), 1160
(w), 1134 (m), 1070 (s), 1026 (m), 994 (w), 856 (s), 826 (s), 778
(m), 748 (m), 672 (m), 644 (w), 586 (m), 624 (w), 586 (w), 490
(w), 426 (w). Anal. Found (calc. for C23H48N3OScSi3): C 52.1
(54.0), H 9.6 (9.5), N 8.4 (8.2)%. Accurate mass EI-MS for
Mes
[C(CH2NSiMe3)2], 25.4 (OCH2CH2), 25.1 (Me of N2 Npy),
20.9 (p-C6H2Me3), 20.1 (o-C6H2Me3), 4.5 (SiMe3), 0.0 (CH2-
SiMe3). IR data (KBr pellet, cmϪ1): 2946 (s), 2914 (s), 2856 (s),
2730 (w), 2662 (w), 1598 (s), 1570 (m), 1476 (s), 1436 (m), 1382
(w), 1358 (w), 1340 (w), 1296 (m), 1230 (s), 1154 (m), 1140 (m),
1120 (w), 1096 (m), 1056 (m), 1018 (m), 992 (w), 956 (w), 854
(s), 816 (w), 782 (m), 748 (m), 728 (w), 706 (w), 694 (w), 680 (m),
646 (w), 604 (w), 560 (w), 534 (w), 442 (w), 406 (w). Anal.
Found (calc. for C35H52N3OScSi): C 69.3 (69.6), H 8.3 (8.6),
N 6.3 (6.9)%.
TMS
fragment [Sc(N2 Npy)]ϩ: Found (calc. for C15H29N3ScSi2)
352.1450 (352.1459).
[Sc(N2TMSNpy)(CH2SiMe3)(THF)] (4) from 1 and
LiCH2SiMe3 (NMR tube scale)
TMS
A solution of [Sc(N2 Npy)Cl(THF)] 1 (21.6 mg, 0.047 mmol)
TMS
and LiCH2SiMe3 (4.4 mg, 0.047 mmol) in C6D6 were trans-
[Sc(N2 Npy)Ph(THF)] (7)
ferred to a 5 mm J. Young NMR tube. The 1H NMR spectrum
TMS
[ScPh3(THF)2] (200 mg, 0.476 mmol) was dissolved in benzene
after 30 min showed quantitative formation of [Sc(N2
-
(15 ml) and cooled to 7 ЊC for the dropwise addition of
Npy)(CH2SiMe3)(THF)] 4.
TMS
H2N2
N
py
(147 mg, 0.476 mmol) in benzene (15 ml). The
resulting yellow solution was allowed to warm to rt and stirred
for 1 h. The volatiles were removed under reduced pressure to
afford 7 as a thermally sensitive, waxy yellow solid. Yield 113
mg (49%).
Tol
[Sc(N2 Npy)(CH2SiMe3)(THF)] (5)
[Sc(CH2SiMe3)3(THF)2] (200 mg, 0.444 mmol) was dissolved in
benzene (20 ml) and cooled to 7 ЊC for the dropwise addition of
Tol
H2N2
N
(153 mg, 0.444 mmol) in benzene (20 ml). The
1H NMR data (C6D6, 500.0 MHz, 298 K): 8.31 [1 H, ddd, H6,
3J (H5H6) = 5.4 Hz, 4J (H4H6) = 1.8 Hz, 5J (H3H6) = 1.2 Hz], 8.20
(2 H, dd, o-C6H5, 3J = 7.6 Hz, 4J = 1.5 Hz), 7.50 (2 H, t, m-C6H5,
py
resulting pale yellow solution was allowed to warm to rt
and stirred for 1 h. The volatiles were removed under reduced
pressure to afford 5 as a yellow solid. Yield 165 mg (68%).
1H NMR data (C6D6, 500.0 MHz, 298 K): 8.86 [1 H, dd, H6,
3J (H5H6) = 5.4 Hz, 4J (H4H6) = 1.5 Hz], 7.10 (4 H, d, o-C6H4Me,
3J = 8.3 Hz), 7.00 [1 H, td, H4, 3J (H3H4H5) = 7.8 Hz, 4J (H4H6) =
3
4
3J = 7.4 Hz), 7.38 (1 H, td, p-C6H5, J = 7.4 Hz, J = 1.5 Hz),
6.94–6.89 (2 H, overlapping m, H3, H4), 6.17 (1 H, m, H5), 3.89
(4 H, br. s, OCH2), 3.78 (2 H, d, CHH, 2J = 12.2 Hz), 3.29 (2 H,
d, CHH, 2J = 12.2 Hz), 1.22 (4 H, br. s, OCH2CH2), 1.20 (3 H, s,
3
TMS
2.0 Hz], 6.91 [1 H, d, H3, J (H3H4) = 8.3 Hz], 6.78 (4 H, d,
Me of N2 Npy), 0.13 (18 H, s, SiMe3). 13C{1H} NMR data
m-C6H4Me, 3J = 8.3 Hz), 6.52 [1 H, ddd, H5, 3J (H4H5) = 7.8 Hz,
(C6D6, 125.7 MHz, 298 K): 163.1 (C2), 147.5 (C6), 138.2 (C4),
137.1 (o-C6H5), 126.9 (m-C6H5), 126.0 (p-C6H5), 120.8 (C5),
120.3 (C3), 72.0 (OCH2), 62.6 (CH2NSiMe3), 48.7 [C(CH2N-
3J (H5H6) = 5.4 Hz, J (H3H5) = 1.5 Hz], 3.76 (4 H, t, OCH2,
4
3J = 6.3 Hz), 3.35 (2 H, d, CHH, J = 12.2 Hz), 3.07 (2 H, d,
2
TMS
CHH, 2J = 12.2 Hz), 2.23 (6 H, s, C6H4Me), 1.26 (3 H, s, Me of
SiMe3)2], 25.2 (OCH2CH2), 25.1 (Me of N2 Npy), 0.5 (SiMe3),
Tol
N2 Npy), 0.92 (4 H, m, OCH2CH2), 0.47 (9 H, s, SiMe3), 0.18
not observed (ipso-C6H5). IR data (NaCl plates, Nujol, cmϪ1):
3196 (w), 3038 (w), 1600 (s), 1570 (m), 1350 (w), 1290 (w),
1246 (s), 1162 (w), 1134 (w), 1070 (m), 1052 (m), 1016 (w),
990 (w), 954 (w), 828 (s), 778 (w), 746 (m), 712 (w), 674 (w),
(2 H, s, CH2SiMe3). 13C{1H} NMR data (C6D6, 125.7 MHz,
298 K): 163.0 (C2), 152.7 (ipso-C6H4Me), 146.2 (C6), 139.0 (C4),
129.8 (o-C6H4Me), 123.4 (p-C6H4Me), 121.7 (C5), 121.4 (C3),
J. Chem. Soc., Dalton Trans., 2002, 4649–4657
4655

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TMS
Table 6 X-Ray data collection and processing parameters for [Sc(N2 Npy)Cl(THF)] 1, [Sc(N2NC2,TMS)Cl(THF)] 2, [Sc2(N2NC3,Me)2(µ-Cl)2] 3,
Mes
Tol
[Sc(N2 Npy)(CH2SiMe3)(THF)]ؒ0.5(Et2O) 6ؒ0.5(Et2O) and [Sc2(N2 Npy)2(CH2SiMe3)2]ؒ4(C7H8) 11ؒ4(C7H8)
1
2
3
6ؒ0.5(Et2O)
11ؒ4(C7H8)
Formula
C19H37ClN3OScSi2
C17H43ClN3OScSi3
C26H66Cl2N6Sc2Si4
C35H52N3OScSiؒ
0.5(C4H10O)
640.93
C54H62N6Sc2Si2ؒ
4(C7H8)
1319.86
Monoclinic
P21/n
Formula weight
Crystal system
Space group
460.11
Orthorhombic
Pbca
470.22
Monoclinic
P21/c
736.02
Triclinic
Triclinic
¯
¯
P1
P1
a/Å
b/Å
c/Å
α/Њ
19.1126(4)
13.1361(2)
19.5217(4)
90
90
90
4901.2(2)
8
0.52
11 144
3439
0.0341, 0.0246
10.5815(2)
21.2366(4)
12.6644(3)
90
110.642(1)
90
2663.2(1)
4
0.52
10.6049(2)
12.1528(2)
16.7295(4)
79.9117(8)
77.1004(9)
77.1029(1)
2030.75(7)
2
0.61
17 186
6361
0.0326, 0.0231
9.2011(2)
10.1961(3)
20.9786(6)
93.499(5)
102.357(5)
103.593(5)
1855.8(1)
2
0.26
10 528
4972
0.056, 0.087
10.7764(1)
15.7709(2)
22.4009(4)
90
93.9372(5)
90
3798.1(1)
2
0.26
β/Њ
γ/Њ
V/Å3
Z
µ(Mo-Kα)/mmϪ1
Total reflections
Observed reflectionsa
9223
4148
0.0395, 0.0312
16 705
4793
0.0433, 0.0257
Rb, Rw
c
a For reflections with I > 3σ(I ). b R = Σ||Fo| Ϫ |Fc||/Σ|Fo|. c Rw = √{Σw(|Fo| Ϫ |Fc|)2/Σw|Fo|2}.
712 (w). Anal. Found (calc. for C25H42N3OScSi2): C 54.6 (59.9),
H 7.6 (8.4), N 8.2 (8.4)%.
(w), 1346 (m), 1332 (w), 1250 (s), 1128 (w), 1072 (s), 1032 (s),
944 (s), 822 (s), 782 (m), 746 (m), 712 (w), 674 (m), 646 (w),
626 (w), 596 (w), 578 (w), 560 (w), 508 (w), 494 (w), 444 (m), 428
(m). Anal. Found (calc. for C21H52N3OScSi4): C 47.3 (48.5), H
9.8 (10.1), N 8.1 (8.1)%.
[Sc(N2NC2,Me)(CH2SiMe3)(THF)] (8)
[Sc(CH2SiMe3)3(THF)2] (200 mg, 0.444 mmol) was dissolved in
benzene (20 ml) and cooled to 7 ЊC for the dropwise addition
of H2N2NC2,Me (116 mg, 0.444 mmol) in benzene (20 ml). The
resulting pale yellow solution was allowed to warm to rt and
stirred for 1 h. The volatiles were removed under reduced pres-
sure to afford 8 as a pale yellow solid. Yield 110 mg (51%).
1H NMR data (C6D6, 500.0 MHz, 298 K): 3.84 (4 H, t,
[Sc(N2NC3,TMS)(CH2SiMe3)(THF)] (10)
To a solution of [Sc(CH2SiMe3)(THF)2] (19.8 mg, 0.044 mmol)
in C6D6 (0.5 ml) was added H2H2NC3,TMS (15.3 mg, 0.044 mmol)
and then transferred to a 5 mm J. Young NMR tube. The
1H NMR spectrum after 30 min showed resonances for [Sc-
(N2NC3,TMS)(CH2SiMe3)(THF)] 10 (assigned by analogy with
those for 8 and 9), SiMe4 and a further equivalent of THF (in
fast exchange with the coordinated THF of 10 on the NMR
timescale). The compound decomposed into a complex mixture
of unidentified products on removal of the volatiles under
reduced pressure.
3
2
OCH2, J = 6.8 Hz), 3.29 (2 H, ddd, NCHH, J = 13.0 Hz,
3
2
3J = 7.4 Hz, J = 4.4 Hz), 3.09 (2 H, dt, NCHH, J = 13.2 Hz,
3J = 5.2 Hz), 2.69 (2 H, ddd, NCHH, 2J = 11.4 Hz, 3J = 5.8 Hz,
3J = 4.4 Hz), 2.34 (2 H, ddd, NCHH, 2J = 12.5 Hz, 3J = 7.3 Hz,
3J = 5.2 Hz), 2.28 (3 H, s, NMe), 1.28 (4 H, t, OCH2CH2,
3J = 6.8 Hz), 0.32 (9 H, s, CH2SiMe3), 0.17 (18 H, s, NSiMe3),
Ϫ0.34 (2 H, s, CH2SiMe3). 13C{1H} NMR data (C6D6, 75.5
MHz, 298 K): 71.1 (OCH2), 61.4 (NCH2), 45.9 (NCH2), 44.3
(NMe), 25.6 (OCH2CH2), 5.1 (CH2SiMe3), 2.6 (CH2SiMe3), 2.2
(NSiMe3). IR data (KBr pellet, cmϪ1): 2948 (s), 2894 (m), 2842
(m), 2812 (m), 2680 (w), 1684 (w), 1594 (m), 1560 (m), 1460 (m),
1400 (w), 1384 (w), 1354 (w), 1242 (s), 1138 (w), 1068 (m), 928
(m), 820 (s), 820 (s), 744 (m), 670 (m), 624 (w), 612 (w), 586 (w),
546 (w), 444 (w), 440 (w), 432 (w), 418 (w). Anal. Found (calc.
for C19H48N3OScSi3): C 49.9 (49.2), H 9.2 (9.1), N 10.4 (10.4)%.
Accurate mass EI-MS for fragment [Sc(N2NC2,Me)]ϩ: Found
(calc. for C11H29N3ScSi2): 304.1456 (304.1459).
1H NMR data (300.2 MHz, C6D6, 298 K): 3.60 (8 H, br. s,
overlapping free and coordinated OCH2), 3.42 (2 H, br. s, CH2),
3.25 (2 H, br. s, CH2), 3.02 (2 H, br. s, CH2), 2.22 (2 H, br. s,
CH2), 1.98 (4 H, br. s, CH2), 1.41 (8 H, br. s, overlapping free
and coordinated OCH2CH2), 1.22 (9 H, s, SiMe3), 1.20 (18 H, s,
amide-SiMe3), 0.1 (9 H, s, amine-SiMe3), 0.0 (27 H, s, SiMe4),
Ϫ0.15 (2 H, s, CH2SiMe3).
Crystal structure determinations of [Sc(N2TMSNpy)Cl(THF)] 1,
[Sc(N2NMeCs 2,TMS)Cl(THF)] 2, [Sc2(N2NC3,Me)2(ꢀ-Cl)2] 3,
[Sc(N2 Npy)(CH2SiMe3)(THF)]ؒ0.5(Et2O) 6ؒ0.5(Et2O) and
Tol
[Sc2(N2 Npy)2(CH2SiMe3)2]ؒ4(C7H8) 11ؒ4(C7H8)
[Sc(N2NC2,TMS)(CH2SiMe3)(THF)] (9)
Crystal data collection and processing parameters are given in
Table 6. Crystals were immersed in a film of inert oil on a glass
fibre and transferred to a KappaCCD diffractometer. Data
were collected at low temperature using Mo-Kα radiation;
equivalent reflections were merged and the images were
processed with the DENZO and SCALEPACK programs.24
Corrections for Lorentz-polarisation effects and absorption
were performed and the structures were solved by direct
methods using SIR92.25 Subsequent difference Fourier syn-
theses revealed the positions of all other non-hydrogen atoms.
Carbon bound hydrogen atoms were placed geometrically and
refined in a riding model. Non-hydrogen atoms were refined
refined anisotropically. For 6ؒ0.5(Et2O) and 11ؒ4(C7H8),
residual electron density was modelled as solvent of crystal-
lisation. Extinction corrections and weighting schemes were
applied as appropriate. Crystallographic calculations were
performed using SIR92,25 the Nonius OpenMoleN package26
and CRYSTALS.27
[Sc(CH2SiMe3)3(THF)2] (147 mg, 0.326 mmol) was dissolved
in benzene (20 ml) and cooled to 7 ЊC for the dropwise addi-
tion of H2N2NC2,TMS (104 mg, 0.326 mmol) in benzene
(20 ml). The resulting colourless solution was allowed to warm
to rt and stirred for 1 h. The volatiles were removed under
reduced pressure to afford 9 as a white solid. Yield 79 mg
(47%).
1H NMR data (C6D6, 500.0 MHz, 298 K): 3.87 (4 H, br. s,
OCH2), 3.54 (2 H, t, NCHH, 2J = 12.4 Hz), 2.98 (2 H, d,
2
2
NCHH, J = 14.2 Hz), 2.89 (2 H, t, NCHH, J = 11.5 Hz),
2
2.33 (2 H, d, NCHH, J = 11.5 Hz), 1.29 (4 H, t, OCH2CH2,
3J = 6.6 Hz), 0.32 (9 H, s, SiMe3), 0.19 (9 H, s, SiMe3), 0.17
(18H, s, amide-SiMe3), Ϫ0.36 (2 H, s, CH2SiMe3). 13C{1H}
NMR data (C6D6, 75.5 MHz, 298 K): 71.0 (OCH2), 60.5
(NCH2), 47.5 (NCH2), 26.0 (OCH2CH2), 5.8 (SiMe3), 2.7
(amide-SiMe3), 0.1 (SiMe3), not observed (CH2SiMe3). IR data
(KBr pellet, cmϪ1): 2954 (s), 2844 (s), 1680 (w), 1448 (m), 1384
4656
J. Chem. Soc., Dalton Trans., 2002, 4649–4657

View Article Online
7 P. Roussel, N. W. Alcock and P. Scott, Chem. Commun., 1998, 801.
8 M. A. Putzer, J. S. Rogers and G. C. Bazan, J. Am. Chem. Soc., 1999,
121, 8112.
9 S. Hajela, W. P. Schaefer and J. E. Bercaw, J. Organomet. Chem.,
1997, 532, 45.
CCDC reference numbers 194287–194291.
See http://www.rsc.org/suppdata/dt/b2/b209382k/ for crystal-
lographic data in CIF or other electronic format.
10 (a) S. C. Lawrence, S. R. Dubberley and P. Mountford, manuscript
in preparation; (b) S. Y. Bylikin, D. A. Robson, N. A. H. Male,
L. H. Rees, P. Mountford and M. Schröder, J. Chem. Soc.,
Dalton Trans., 2001, 170; (c) M. E. G. Skinner, B. R. Tyrrell,
B. D. Ward and P. Mountford, J. Organomet. Chem., 2002, 647,
145; (d ) M. E. G. Skinner and P. Mountford, J. Chem. Soc.,
Dalton Trans., 2002, 1694.
Acknowledgements
We thank the EPSRC, Leverhulme Trust, Royal Society, British
Council, CNRS and the Institut Universitaire de France
for support, and Dr G. A. Vaughan (Exxon Chemical Co.)
for generous gifts of ScCl3. We acknowledge the solution of
the crystal structure of compound 6 by Natalie Gruber and
André DeCian (Strasbourg) and thank Lydie Antonietti for
experimental help.
11 M. E. G. Skinner, D. A. Cowhig and P. Mountford,
Chem. Commun., 2000, 1167; M. E. G. Skinner, Y. Li and
P. Mountford, Inorg. Chem., 2002, 41, 1110.
12 For
a
review and leading references see L. H. Gade,
Chem. Commun., 2000, 173 (feature article).
13 S. Friedrich, M. Schubart, L. H. Gade, I. J. Scowen, A. J. Edwards
and M. McPartlin, Chem. Ber./Recueil, 1997, 130, 1751.
14 P. Mehrkhodavandi, P. J. Bonitatebus Jr. and R. R. Schrock,
J. Am. Chem. Soc., 2000, 122, 7841; J. P. Araujo, D. K. Wicht,
R. R. Schrock and P. J. Bonitatebus, Organometallics, 2001, 20,
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15 N. Emig, H. Nguyen, H. Krautscheid, R. Reau, J. Cazaux and
G. Bertrand, Organometallics, 1998, 17, 3599.
16 F. G. N. Cloke, P. B. Hitchcock and J. B. Love, J. Chem. Soc.,
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